This invention relates to GaAs semiconductor devices and, more particularly, to improvement of refractory passivated GaAs ohmic contacts by ion implantation.
Heretofore ohmic contacts for GaAs FET devices have used an AuGeNi layer on GaAs wherein the AuGe Ni-GaAs device is heated to the point that the AuGeNi layer and adjacent area of the GaAs melts. Once they have melted, the germanium diffuses into the GaAs to form with the GaAs an ohmic contact with increased carrier concentration that induces tunneling. The ohmic contact is not always reliable-it shows island formations or balling-up and deterioration with aging.
A TiW passivation layer has been deposited on epitaxial silicon structures which deteriorate with age and high temperature operation.
U.S. Pat. No. 3,909,307 implants doping atoms into a thin epitaxial layer of silicon on a substrate so that they are along the boundary layer. The atoms reduce or eliminate boundary charges which normally occur during growth.